Solid-liquid Interactions and Interfacial Water Structuring Determine Slip and Drag in Turbulent Boundary Layer Flows

流体摩擦和阻力是一种普遍存在的现象，在运输系统中尤其重要。流体阻力是一种能源消耗障碍，在地球仪上运输人员和货物的承运人必须不断克服这一障碍;因此，减少流体阻力不仅可以转化为更有效和可行的运输系统，还可以转化为更环保的船舶。增加与水接触的固体表面处的流体滑移是一种潜在的减阻机制。表面工程可以用来产生滑移面，然而，在湍流滑移的基本机制还没有得到很好的理解。因此，本项目的主要目标是使用先进的建模技术和实验相结合的水动力滑动的机制进行基本调查。该项目还将创建一个面向公众的播客，调查人员将以坦率和可访问的方式向公众介绍他们的调查结果。研究生和本科生将参与该项目的研究和推广活动，促进公平和包容代表性不足的人口将被定为一项使命，该项目的目标是弥合高剪切率流动中流体动力学滑移的实验观察与数值/理论计算之间的知识差距。同样，通过结合表面表征技术和不同长度尺度的数值模拟，将解决滑移的微观机制和宏观阻力计算之间的概念不匹配问题。为实现这些目标：㈠分子动力学模拟和理论将用于建立固体-水界面的物理模型，能够计算流体动力学滑移和界面水结构; ㈡和频产生振动光谱和原子力显微镜将用于验证滑移计算，而且还验证界面液体性质与滑移计算的关系;以及（iii）将首次使用直接数值模拟和壁面模拟大涡模拟，利用物理信息边界条件模拟阻力，以进一步促进低阻力工程表面的设计。该项目的研究成果将推动流体动力学和表面科学领域的发展，特别是在减阻对降低能耗至关重要的领域。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Fluid friction and drag are ever-present phenomena, and particularly important issues in transportation systems. Fluid drag is an energy consumption barrier that must be continuously overcome by carriers transporting people and goods across the globe; thus, reducing fluid drag translates not only into more effective and viable transportation systems, but also in more ecofriendly ships. Increasing fluid slip at solid surfaces in contact with water is a potential drag-reduction mechanism. Surface engineering can be used to generate slip-surfaces; however, the fundamental mechanisms of slip in turbulent flows are not well understood. Therefore, the main objective of this project is to conduct a fundamental investigation into the mechanisms of hydrodynamic slip using a combination of sophisticated modeling techniques and experiments. This project will also create a general-public-oriented podcast where the investigators will present their findings to the public in a candid and accessible manner. Graduate and undergraduate students will be involved in the research and outreach activities of the project, where the promotion of equity and inclusion of underrepresented populations will be set as a mission.The goal of this project is to bridge the knowledge gap between experimental observations and numerical/theoretical calculations of hydrodynamic slip in high-shear rate flows. Similarly, through the combination of surface characterization techniques and numerical simulations at different length scales, the conceptual mismatch between the microscopic mechanisms of slip and macroscopic drag calculations will be addressed. To achieve these goals: (i) molecular dynamics simulations and theory will be used to create physics-informed models of solid-water interfaces able to calculate hydrodynamic slip and interfacial water structuring; (ii) sum frequency generation vibrational spectroscopy and atomic force microscopy will be used to validate not only the slip calculations, but also to verify the interfacial liquid property relation to slip calculations; and (iii) direct numerical simulations and wall modeled large eddy simulations will be used for the first time to model drag using physics-informed boundary conditions to further contribute to the design of engineered surfaces with low drag. The research output from this project will advance the fields of fluid dynamics and surface science, particularly in areas where drag reduction is paramount for the reduction of energy consumption.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.